Hidden Companions to Intermediate-mass Stars. X. Solving for the Mass Ratio in the Spectroscopic Binary Zubenelgenubi = α <SUP>2</SUP> Librae

• Waisberg, Idel
;
• Klein, Ygal
;
• Katz, Boaz

Abstract

Zubenelgenubi = α ² Librae is a nearby double-lined spectroscopic binary that forms a quadruple system with α ¹ Librae. The radial velocity amplitude for the rapidly rotating primary is subject to a systematic uncertainty and as a result only a lower limit q = 0.81 to the mass ratio has been previously reported. Here we present a VLTI/GRAVITY interferometric observation of Zubenelgenubi in which we measured a K band flux ratio of 74.7%, resulting in isochrone masses M _Aa = 1.95 M _⊙ and M _Ab = 1.79 M _⊙ (q = 0.92). The fact that the projected rotational velocities differ by a factor of three despite the similar masses suggests that the stellar spin axes are significantly misaligned in spite of the small semimajor axis a = 0.52 au or alternatively that the primary is a merger product. *Based on observations collected at the European Southern Observatory, Chile, Program ID 111.24UP.001.